Technical Field
The present invention relates to a printing cylinder assembly for a printing machine in which a printing cylinder whose diameter is variable is used to produce printed images that are different in their vertical length.
Background Art
A printing machine designed to print on a continuous sheet or web of paper, printed images which are different in vertical length has been disclosed in JP 2004-74526 A.
Such printing machines are known as a sleeve cylinder exchangeable variable printer, in which a printing cylinder comprises a sleeve cylinder removably mounted on the rotating shaft so that it can be fitted on, and be extracted from, the rotating shaft. A plurality of sleeve cylinders of different diameters are prepared for printing images of different vertical lengths and a sleeve cylinder is selected which is of a particular diameter that meets with a particular vertical size of an image to be printed. Each of such sleeve cylinders is mounted on the rotating shaft to print on a continuous sheet or web of paper print images different in vertical length.
To enable a sleeve cylinder to be exchanged in the conventional printing cylinder assembly described above in which the sleeve cylinder is removably mounted on the rotating shaft so that it can be fitted on and be extracted from the rotating shaft, it is necessary to couple the sleeve cylinder and the rotating shaft together so that the sleeve cylinder may not move axially or rotate around the rotating shaft but may be rotated integrally with the rotating shaft, and by releasing the coupling to decouple the sleeve cylinder from the rotating shaft so that the sleeve cylinder may be extracted from the rotating shaft and be replaced by another sleeve cylinder to be fitted on the rotating shaft.
However, making the assembly capable of fitting a sleeve cylinder on, and extracting it from, a rotating shaft in a conventional manner, tends to cause a backlash and axial deflection of the sleeve cylinder.
In view of such problems in the prior art, it is an object of the present invention to provide a printing cylinder assembly for a printing machine which ensures that a sleeve cylinder for removably mounting on a rotating shaft so that it can be fitted on and extracted therefrom be firmly coupled to the rotating shaft, without causing a possible backlash and axial deflection of the sleeve cylinder and yet permitting it to be readily decoupled.